| Property | Summary |
|---|---|
| Gene name | **ARG1** (arginase 1) (pqac-00000000, pqac-00000009) |
| UniProt accession | **P05089** (user-provided target specification) |
| EC number | **EC 3.5.3.1** (pqac-00000001) |
| Protein mass | Mature enzyme is described as a **~105 kDa homotrimer** with **~35 kDa subunits**; some reviews also report **~130 kDa** total trimer mass depending on construct/annotation conventions (pqac-00000001, pqac-00000027, pqac-00000028) |
| Quaternary structure | **Homotrimeric metalloenzyme**; trimerization is required for full catalytic activity, and monomerization causes major loss of activity (>90%) (pqac-00000001, pqac-00000023, pqac-00000026) |
| Subcellular localization | **Cytosol** (especially hepatocyte cytosol); distinct from mitochondrial ARG2 (pqac-00000002, pqac-00000010, pqac-00000012, pqac-00000014) |
| Primary tissue expression | **Predominantly liver**, especially **periportal/zone 1 hepatocytes**; also detected in erythrocytes, vasculature, and immune cells such as M2-like macrophages (pqac-00000009, pqac-00000011, pqac-00000013) |
| Catalytic cofactor | **Binuclear Mn2+ center** with two manganese ions in each active site, bridged by hydroxide/water during catalysis (pqac-00000002, pqac-00000003, pqac-00000027) |
| Substrate | **L-arginine** is the physiological substrate; wild-type human ARG1 does **not efficiently hydrolyze agmatine** (pqac-00000002, pqac-00000046, pqac-00000047, pqac-00000048) |
| Products | **L-ornithine + urea** (pqac-00000001, pqac-00000002, pqac-00000006) |
| Km value | **Km ~3.3 mM** for ARG1 under the reported assay conditions (pH 7.4) (pqac-00000004, pqac-00000059) |
| Reaction catalyzed | **Hydrolysis of L-arginine to L-ornithine and urea**; final step of the hepatic urea cycle and a key branchpoint in arginine metabolism (pqac-00000001, pqac-00000006, pqac-00000010) |
| Key disease associations | **Arginase deficiency / argininemia** (strong genetic disease association), plus links to **cancer immune suppression/tumor microenvironment**, and Open Targets associations with **hereditary disease**, **type 2 diabetes mellitus**, and **obesity disorder** (pqac-00000029, pqac-00000030, pqac-00000035, pqac-00000038, pqac-00000039, pqac-00000000) |


*Table: This table summarizes core biochemical, structural, localization, and disease-related properties of human Arginase-1 (ARG1/P05089). It is useful as a compact reference for functional annotation and interpretation of disease relevance.*